1. Field of the Invention
This invention relates in general to electronic assemblies, and, in particular, to a micro-fixtured lensed assembly for optoelectronic devices and optical fibers.
2. Description of Related Art
Optoelectronics and fiber optic communications are commonly used in communications and electronic devices. The use of optical fibers for telephonic and other information transfer is desirable because of the high bandwidth and high data rates possible with fiber optic lines. The electronics that transmit and receive the light signals that travel on fiber optic lines have become integrated with the fiber optic lines for better signal transmission and reception.
Alignment between the individual strands of a fiber optic cable and the detectors and transmitters is crucial to a fiber optic data transmission system. There are typically two approaches to alignment of the fiber to the electronics; active approaches, where light is passed through the fiber and strikes the detector, and the detector is monitored during positioning of the fiber in relation to the detector, and passive approaches, where no light is passed through the fiber, and mechanical devices are used for alignment of the individual parts of the transmitter or receiver assembly.
Previous passive alignment approaches directly couple light between a fiber and an optoelectronic device without passing that light through a separate optical lens. As a result, divergence of the optical beam and differences in the optical-mode sizes can reduce the optical coupling efficiency.
FIG. 1 illustrates an optoelectronic transmitter assembly of the related art. As shown, assembly 100 comprises a silicon platform 102, also called a silicon waferboard, and a laser chip 104. Grooves 106 are etched into the silicon platform 102 for mechanically holding optical fibers against the silicon platform 102 and for aligning the optical fibers to the laser chip 104. The grooves 106 are typically v-shaped. The silicon platform 102 also contains pedestals 108, typically nine microns high, formed by reactive ion etching (RIE) into the top surface of the silicon. The pedestals 108 serve to position the laser chip 104 on the plane of the silicon platform 102.
A notch 110 is etched into laser chip 104, and the notch is placed against one pedestal 108, while the cleaved front facet 112 is placed against two other pedestals 114. Standoffs 116 are constructed from polyimide of a controlled thickness, typically five microns, and patterned by RIE. The standoffs 116 determine the vertical position of the laser chip 104 which is mounted with the laser devices down, facing the silicon platform 102.
FIGS. 2A-2B illustrate another device of the related art. The device 200 of FIGS. 2A-2B illustrate a silicon platform 202 with a photodetector array 204 where the photodetector array 204 is mounted with the photodetectors facing away from the silicon platform 202. Grooves 206 and ribbon support 208 are etched into the silicon platform 202 to mechanically support the fiber optic cables and the individual optical fibers. As described with respect to FIG. 1, the photodetector array 204 is positioned and aligned by pressing the photodetector array 204 against pedestals 210 that have been etched into the surface of silicon platform 202. However, the photodetector size must be larger than necessary to accommodate the alignment tolerances, inaccuracies in dicing and/or cleaving of the photodetector array 204, and divergence of the light beam before it reaches the photodetector array 204, thus limiting the bandwidth of the output.
FIG. 2B illustrates the light path 212 of the device illustrated in FIG. 2A. Grooves 206 are typically v-shaped, and terminate in reflective mirror surfaces 214 that redirect the light from an optical fiber out of the plane of the silicon platform 202 and onto the backside of the photodetector array 204. Wire bonds 216 carry the signals generated by photodetector array 204 to other circuitry.
FIG. 3 illustrates a laser array of the related art. Device 300 again has a silicon platform 302 and laser array chip 304 mounted to silicon platform 302. Laser array chip 304 is an edge emitting laser array, and the optical fibers 306 are guided through a structure 308 in silicon platform 302 to in-plane optical elements 310 formed directly on the silicon platform 302. The tapered waveguides 312 transform the small diameter of the optical mode in the edge-emitting laser 304 to the larger diameter of the optical mode in the optical fiber 306. The tapered waveguides 312 are formed from the thin films of silica deposited on the silicon platform 302 surface. The optical fibers 306 are held in v-grooves etched in the silicon platform 302. Since both the tapered waveguides 312 and the v-grooves are fabricated directly on the silicon platform 302, their relative positions can be controlled precisely. The laser chip is mounted onto the silicon platform 302 by means of solder bumps 314 and standoffs 316, which also align the chip on the silicon platform 302. However, this approach suffers from having the optical elements formed as an integral part of the silicon platform 302, thereby reducing the types of optical elements that can be used in the assembly 300.
There is therefore a need in the art for an apparatus and method for aligning optical fibers to optoelectronic devices. There is also a need in the art for a method of aligning optical fibers to optoelectronic devices that reduces manufacturing time and costs. There is also a need in the art for a method of aligning optical fibers to optoelectronic devices that maximizes the throughput of the optical fiber.
The present invention discloses a method and apparatus for aligning an optical fiber to an optoelectronic element. The apparatus comprises a base and a lens. The base is fabricated from a first crystallographic orientation, and includes an alignment feature for an optical fiber. The lens is fabricated from a second crystallographic orientation, and is aligned with the base using a second alignment feature associated with the first and second crystallographic orientations.
A method in accordance with the present invention comprises the steps of coupling an optoelectronic element to a base comprising a material having a first crystallographic orientation, coupling a lens to the base, the lens comprising a material having a second crystallographic orientation, wherein the lens is aligned to the base using the first crystallographic orientation and the second crystallographic orientation, and attaching an optical fiber to the base, wherein the optical fiber is placed proximate to the lens, such that a light path of the optical fiber is aligned with the optoelectronic element through the lens.
An optoelectronic assembly in accordance with the present invention comprises an optoelectronic element, a lens assembly, and a base. The optoelectronic element converts between an optical signal and an electrical signal. The lens assembly comprises a first material having a first crystallographic orientation and includes a first alignment feature. The base comprises a second material having a second crystallographic orientation and includes a second alignment feature. The lens assembly and base are aligned using the first alignment feature and the second alignment feature, the first alignment feature aligns the lens assembly to the optoelectronic element, and the second alignment feature aligns an optical fiber to the lens assembly.
The present invention provides an apparatus and method for aligning optical fibers to optoelectronic devices. The present invention also provides a method of aligning optical fibers to optoelectronic devices that reduces manufacturing time and costs. Further, the present invention provides a method of aligning optical fibers to optoelectronic devices that maximizes the throughput of the optical fiber.